[AMPS] HV Power Supply Project Example.

nospam4me@juno.com nospam4me@juno.com
Tue, 8 May 2001 23:57:03 -0700

RE: HV Power Supply Project Example. 
Hello from the Rotating Blackout zone... 
I'm here to describe a High Voltage Power Supply 
I've completed from mostly surplus parts.  The 
pictures should prove one can build a HV supply 
for cheap money, serving in SSB  Amplifier ps 
service. Inventive part mounting hints are shown 
that one might not normally think about. The power 
supply case is a recycled computer tower. 
This is a rather unconventional way of showing 
this project via the amps list server. If your not 
interested in the project or the pictures, just 
delete this Email.   Onward... 
One can often find surplus transformers cheap, I've 
seen a very common Collins Brand HV unit with dual 
primaries, 2250 volt CT secondary @ ~500mA  
removed from surplus transmitters.  I've been able to 
pick up a few through the years and figured it was 
about time to use one.  The secondary has a pretty 
low resistance which lends it's use in doubler service 
if desired.  Surplus transformers are made like old 
battle ships... big and heavy. This one's no exception. 
Mounting of surplus transformers can sometimes 
be a real hardware pain.  The common bottom 
stud bolted packages with same end connections 
require extra layout considerations.  I simply avoid 
all the extra hardware by laying this style of xmfr 
sideways, using a thick aluminum bracket to anchor 
one side end down to the box bottom. Underneath is 
a thin sheet of cut plywood cleaned and spray painted 
gray to serve as a simple shock absorber.  1/4 inch 
bolts are used and an ear bracket on the back wall 
ensures the xmfr stays in position. A very solid 
mount.  I found the thin sheet of painted kiln dried 
plywood idea was originally used in WWII aircraft 
power supplies.  The bottom bracket holds the wood 
in place using 1/4 inch hardware. 
Finding a great case or cabinet is as close as your 
local Computer Surplus Parts Location.  I've been 
eye balling an old Compac 386 server case for some 
time, when this project hit the burner... the case fit 
the bill with minimal modification.  I removed the 
internals which included the AC supply and covered 
the large supply hole with a suck out fan. A perfect 
fit.  Many available vent holes are located around 
the box for air inlet.
The card slot holes were covered with original blank 
slot covers and the keyboard/mouse hole areas 
made a great place to place a plastic cover for HV 
wire exit/entrance.  The large AC cord is through a 
chassis mounted strain relief.  
The filter bank and diode boards were once part of a 
very large and hefty Erbtec 6kv power supply.  A trip to 
the band saw separated the diode sections away 
from the two separate filter banks. I obtained the 
board for surplus weight prices off a popular on line 
auction service.  I'm under the impression one of 
our trusty amps members had something to do 
with the original Erbtec board design. It was a serious 
3 phase power supply in its day. 
Large square plastic blocks mount the boards in 
place, you can see the cut diode board on the cab 
bottom spacers.  The GI Brand diodes are rated at 
better than 3amp 6kv... wish I could find the source 
for these "microwave oven spec units."  The white 
door knob bypass cap was scrounged surplus from 
a laser ps.  The poly plastic blocks were cut from 
surplus material.  Poly plastic is sold locally by 
the pound at the surplus supply store. 
The frame hole left by the original computer drive 
bay makes an ideal front panel control location. A 
square cut sheet of thick aluminum makes a nice 
strong switch/metering/indicator mount.
A dual tied AC breaker switch, lamps meter and 
metering points are placed on the front panel. 
So it all went in the one box which fired up without 
a hitch. Here the zero to 10KV meter shows almost 
7KV no-load during initial testing. The indicator 
lamps have not been wired yet. 
The original ps supply couldn't have fit the bill 
any better. Large non inductive resistors were used 
in the original circuit, so I moved things around 
and set up this 200 watt 15 ohm resistor for neg 
lead metering. The ps ground connection to the 
case is made with large ground braid. You can see 
the fan in the back.  Each of the cap bleeders are 
100K 5 watt metal film resistors.  Two on each 
capacitor for equiv 50K ohm. 
Put it all in place and get the last cover ready, 
then snap a picture or two...
here's the circuit details: 
Set up as a voltage doubler with a terminal 
jack board to allow change over to a bridge 
16, 450 volt hand matched capacitors in series 
with 50K of bleeder resistance across each. 
Each cap is surge rated to 525 Vdc. 
Negative lead current metering through a 15 
ohm 200 watt resistor. Front panel metered 
zero to 10kv.  Front panel AC on and cap bank 
charged indication.  Glitch resistors and 
diodes along with bypass caps in place. 
Front panel test point metering at chassis 
ground, negative return and the hv divided 
by 100.  The red HV wire is rated to 40KV...
With covers on, has same profile as the original 
Compac Server box it once was.  Works very 
well.   Total cost, less than $100  Circuit 
diagram available free upon request. Now 
in service in a high speed pulser research 
project,  then it's off to amplifier service when 
that project is completed. 

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